JP2012124275A - Solid-state imaging device, method for manufacturing the same, and electronic apparatus provided with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solid-state imaging device which is capable of reducing the darkening of an output image, a method for manufacturing the same, and an electronic apparatus provided with the same.SOLUTION: The solid-state imaging device comprises an imaging unit 10 in which an effective pixel region A and an optical black region B are formed. An antireflection film 36 is formed on a sensor unit 11a in the effective pixel region A, while an antireflection film is not formed on a sensor unit 11b in the optical black region B.

Description

  The present invention relates to a solid-state imaging device, a manufacturing method thereof, and an electronic apparatus including the solid-state imaging device, and in particular, a solid-state imaging device having an effective pixel region and an optical black region, a manufacturing method thereof, and the solid-state imaging device. It is related with the provided electronic equipment.

  FIG. 4 is a cross-sectional view showing an imaging unit 100 of a conventional solid-state imaging device. As shown in FIG. 4, the imaging unit 100 includes an antireflection film 136 made of a silicon nitride film on a sensor unit 111 made of silicon (Si) or the like formed on the semiconductor substrate 101 with a silicon oxide film 102 interposed therebetween. It is formed. The antireflection film 136 is formed on the sensor unit 111 in each of the effective pixel area A and the optical black area (OB area) B. Further, the entire OB region B is covered with the light shielding film 104.

  Normally, the refractive index of the silicon nitride film (antireflection film 136) is higher than the refractive index of the silicon oxide film 102. Therefore, the light reflected at the interface between the sensor unit 111 and the silicon oxide film 132 is re-reflected by the silicon oxide film 102 and the antireflection film 136. As a result, reflection of light incident on the sensor unit 111 at the interface of the sensor unit 111 is reduced. Thereby, by providing the antireflection film 136, the light collection rate of the sensor unit 111 is improved. Therefore, an effect of improving the sensitivity of the solid-state image sensor can be obtained.

  On the other hand, Patent Document 2 discloses a solid-state imaging device in which an antireflection film is formed only in the OB region.

JP-A-10-178166 (released on June 30, 1998) JP-A-7-130975 (published May 19, 1995)

  However, the conventional solid-state imaging device has a problem that the output image becomes dark because the dark current in the OB region increases.

  Specifically, in the solid-state imaging device, electric charges are generated even when no light is incident on the sensor unit 111 due to the remaining of some surface states. This charge is called “dark current”. Therefore, in the manufacturing process of the solid-state imaging device, a hydrogen sintering process (annealing process) is performed in order to reduce this dark current.

  However, while the antireflection film 136 is intended to improve the sensitivity of the solid-state imaging device, it has a property of preventing hydrogen from entering. For this reason, the antireflection film 136 reduces the effect of the hydrogen sintering process (hydrogen sintering effect).

  As shown in FIG. 4, normally, the opening 138b formed in the light shielding film 135 on the sensor unit 111 in the OB region B is smaller than the opening 138a formed in the light shielding film 135 on the sensor unit 111 in the effective pixel region A. . For this reason, the hydrogen sintering effect in the OB region B is more easily reduced, and the dark current in the OB region is increased. For example, FIG. 5 is a graph showing a high-temperature (80 ° C.) dark current value in a conventional solid-state imaging device including the imaging unit of FIG. As shown in FIG. 5, the dark current value in the OB region increases at high temperatures (80 ° C.). The OB area B is used as a reference for the black level of the solid-state imaging device. For this reason, when the dark current value in the OB area B increases, even if the effective pixel area A is exposed to light, the signal level (black sun) is as if the light is not irradiated. As a result, the output image becomes dark.

  Patent Document 2 describes that the dark current level difference between the effective pixel region and the OB region can be eliminated by forming an antireflection film (hydrogen blocking film) in the OB region. Generally, the light shielding film is formed of a metal film such as tungsten (W) or aluminum (Al). This light-shielding film (particularly the W film) is formed on the anti-peeling film after previously forming an anti-peeling film (for example, a TiN film) of the light-shielding film. However, the peeling prevention film has a property of preventing entry of hydrogen. For this reason, the effect of the hydrogen sintering process (hydrogen sintering effect) is reduced, and the dark current in the OB region is increased. Therefore, in the configuration of Patent Document 2, the dark current value in the OB region further increases.

  Therefore, the present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide a solid-state imaging device capable of reducing the darkness of an output image, a manufacturing method thereof, and the solid-state imaging. An object of the present invention is to provide an electronic device including an element.

  In order to solve the above problems, a solid-state imaging device according to the present invention includes an imaging unit in which an effective pixel region and an optical black region are formed, and each region of the effective pixel region and the optical black region includes: In the solid-state imaging device in which the light receiving portion is formed, an antireflection film is formed on the light receiving portion in the effective pixel region, while an antireflection film is not formed on the light receiving portion in the optical black region. It is a feature.

  According to the above configuration, the antireflection film is formed only on the light receiving portion formed in the effective pixel region in the effective pixel region and the optical region (OB region), and on the light receiving portion in the OB region. An antireflection film is not formed. For this reason, the hydrogen sintering effect of the OB region where the antireflection film is not formed is improved. Thereby, the increase (deterioration) of the dark current in the OB region that occurs at a high temperature (about 80 ° C.) can be suppressed. That is, the level difference of the dark current in the light receiving portion between the effective pixel region and the OB region is reduced. Therefore, it is possible to reduce the darkness of the output image due to the dark current.

  In the solid-state imaging device according to the present invention, the antireflection film is preferably a silicon nitride film.

  According to said structure, the antireflection film is formed from the silicon nitride film (SiN film). For this reason, the antireflection film effectively re-reflects the light reflected by the light receiving portion in the effective pixel region, and the light collection rate of the light receiving portion in the effective pixel region can be further improved. Therefore, it is possible to improve the hydrogen sintering effect of the OB region while improving the sensitivity of the light receiving unit in the effective pixel region.

  In order to solve the above problems, a method for manufacturing a solid-state imaging device according to the present invention includes an imaging unit in which an effective pixel region and an optical black region are formed, and each region of the effective pixel region and the optical black region. In the method of manufacturing a solid-state imaging device in which a light receiving portion is formed, a reflection that does not form an antireflection film on the light receiving portion in the optical black region while an antireflection film is formed on the light receiving portion in the effective pixel region. It is characterized by having a prevention film forming step.

  According to the above method, in the antireflection film forming step, the antireflection film is formed only on the light receiving portion formed in the effective pixel region among the effective pixel region and the optical region (OB region). An antireflection film is not formed on the light receiving portion. For this reason, the hydrogen sintering effect of the OB region where the antireflection film is not formed is improved. Thereby, the increase (deterioration) of the dark current in the OB region that occurs at a high temperature (about 80 ° C.) can be suppressed. That is, the level difference of the dark current in the light receiving portion between the effective pixel region and the OB region is reduced. Therefore, it is possible to manufacture a solid-state imaging device that can reduce the darkness of the output image due to the dark current.

  The method for manufacturing a solid-state imaging device according to the present invention further includes a light shielding film forming step for forming a light shielding film over the entire optical black region, and a hydrogen sintering treatment step for performing a hydrogen sintering treatment, and the hydrogen sintering treatment step. It is preferable to perform the said light shielding film formation process after this.

  According to the above method, the hydrogen sintering process is performed before the light-shielding film that hardly transmits hydrogen is formed in the entire OB region. Thereby, the hydrogen sintering process increases the sintering effect of hydrogen in the OB region. As a result, an increase in dark current in the OB region can be reduced. Therefore, it is possible to more reliably reduce the output image from being darkened by the dark current.

  In the method for manufacturing a solid-state imaging device according to the present invention, it is preferable that the antireflection film forming step forms an antireflection film by a plasma CVD method or a low pressure CVD method.

  According to the above method, the antireflection film is formed by the plasma CVD method or the low pressure CVD method. Accordingly, it is possible to form an antireflection film that can effectively re-reflect the light reflected by the light receiving portion in the effective pixel region and further improve the light collection rate of the light receiving portion in the effective pixel region. Therefore, it is possible to improve the hydrogen sintering effect of the OB region while improving the sensitivity of the light receiving unit in the effective pixel region.

  In order to solve the above-described problems, an electronic apparatus according to the present invention includes any one of the solid-state imaging elements described above. Therefore, it is possible to provide an electronic apparatus including a solid-state imaging device that can reduce the darkness of an output image due to a dark current.

  As described above, in the solid-state imaging device according to the present invention, the antireflection film is formed on the light receiving part in the effective pixel region, while the antireflection film is not formed on the light receiving part in the optical black region. It is a configuration. Therefore, it is possible to reduce the darkness of the output image due to the dark current.

It is sectional drawing which shows the imaging part of the solid-state image sensor which concerns on this invention. It is sectional drawing which shows the manufacturing process of the solid-state image sensor of this invention. It is a graph which shows the dark current value of the solid-state image sensor of this invention. It is sectional drawing which shows the imaging part of the conventional solid-state image sensor. It is a graph which shows the dark current value of the conventional solid-state image sensor.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[Embodiment 1]
(1) Solid-State Imaging Device FIG. 1 is a cross-sectional view showing an imaging unit 10 of the solid-state imaging device of the present invention. As shown in FIG. 1, the imaging unit 10 is formed with an effective pixel area A that requires light reception and an optical black area (OB area) B for defining the black level. The imaging unit 10 has a configuration in which a charge transfer unit (vertical transfer unit) 3 is formed on a semiconductor substrate (substrate) 1 via a first oxide film 2. The entire OB region B is covered with the light shielding film 4 (first light shielding film).

  Although not shown, the solid-state imaging device of the present embodiment includes a horizontal transfer unit (HCCD) having a CCD structure and an output unit connected to the horizontal transfer unit in addition to the imaging unit 10. That is, the solid-state imaging device of the present embodiment is a so-called interline transfer (IT) type CCD image sensor. For convenience of explanation, the light shielding film 4 side is the upper side, and the semiconductor substrate 1 side is the lower side.

  In the following description, when distinguishing the members formed in the effective pixel region A and the OB region B, “a” is added to the end of the member number formed in the effective pixel region A, and the member is formed in the OB region B. “B” is added to the end of the member number. On the other hand, if not distinguished, “a” and “b” are not added to the end of the member number.

  The semiconductor substrate 1 is composed of a P-type silicon substrate or the like. On the semiconductor substrate 1, a sensor unit (light receiving unit, photodiode unit) 11, a vertical transfer unit (VCCD) 12, and a semiconductor layer 13 are formed.

  The sensor unit 11 is a photoelectric conversion unit in which a plurality of light receiving elements (photodiodes) are arranged in a two-dimensional matrix. The vertical transfer unit 12 is provided corresponding to each light receiving element of the sensor unit 11. The vertical transfer unit 12 functions as a transfer region that transfers charges generated in the light receiving element in the vertical direction. The semiconductor layer 13 is formed between the sensor unit 11 and the vertical transfer unit 12. The semiconductor layer 13 functions as a readout region for reading out charges generated in the sensor unit 11 (light receiving element) to the vertical transfer unit 12. When the semiconductor substrate 1 is a P-type semiconductor substrate, the sensor unit 11 and the vertical transfer unit 12 are N-type semiconductor regions (N-type diffusion regions; CCD diffusion regions), and the semiconductor layer 13 is a P-type semiconductor region (P well). Area).

  The first oxide film 2 is formed over the entire light receiving surface of the semiconductor substrate 1. The first oxide film 2 is an insulating film such as a silicon oxide film. The first oxide film 2 may be a single layer film or a multilayer film.

  The charge transfer unit 3 is formed on the first oxide film 2. The charge transfer unit 3 includes a gate electrode unit 31 (gate insulating film 32 and gate electrode 33), a second oxide film 34, a light shielding film 35 (second light shielding film), an antireflection film 36, and a third oxide film 37. Has been.

  The gate electrode part 31 is formed on the vertical transfer part 12 of the first oxide film 2. The gate electrode portion 31 is composed of a gate insulating film 32 and a gate electrode 33. The gate insulating film 32 is formed on the first oxide film 2, and the gate electrode 33 is stacked on the gate insulating film 32.

  The second oxide film 34 is formed of an insulating film such as a silicon oxide film and covers the gate electrode portion 31. The second oxide film 34 serves to insulate the gate electrode 33 from the light shielding film 35 and to improve the adhesion of the light shielding film 35 formed on the second oxide film 34.

  The light shielding film 35 is formed of a metal film such as tungsten or aluminum, and covers the second oxide film 34. The light shielding film 35 shields the gate electrode portion 31 from light.

  The second oxide film 34 and the light shielding film 35 have a light receiving opening 38. The opening 38 is formed on the sensor unit 11, and the first oxide film 2 is exposed in the region where the opening 38 is formed. Thereby, incident light enters the incident surface of the sensor unit 11 through the opening 38. Note that the area of the opening 38a in the effective pixel region A is larger than the area of the opening 38b in the OB region.

  The antireflection film 36 is formed only on the sensor unit 11a in the effective pixel region A. Specifically, the antireflection film 36 is formed on the first oxide film 2 exposed from the opening 38a. The antireflection film 36 is provided in the opening 38a and reduces reflection on the light incident surface of the sensor unit 11a.

As the antireflection film 36, a silicon nitride film such as Si ₃ N _{4 or} a titanium nitride film such as TiON or TiN can be used. The silicon nitride film is a film that blocks the permeation of hydrogen, and the TiON film is a film that adsorbs hydrogen, and both block the diffusion of hydrogen to the sensor unit 11.

  The third oxide film 37 is formed of an insulating film such as a silicon oxide film, and is provided for insulation between the light shielding film 4 and the light shielding film 35. The third oxide film 37 also functions as a planarizing film for the charge transfer unit 3. The first oxide film 2, the second oxide film 34, and the third oxide film 37 may be the same insulating film or different insulating films.

  The light shielding film 4 is formed over the entire OB region B. As with the light shielding film 35, the light shielding film 4 is formed of a metal film such as tungsten or aluminum. The light shielding film 4 and the light shielding film 35 may be the same metal film or different metal films.

  A planarizing film 5 is formed on the third oxide film 37 and the light shielding film 4. As the planarizing film 5, for example, a step preventing film for forming a color filter can be used.

  As described above, the solid-state imaging device of the present embodiment has basically the same configuration as the solid-state imaging device described in Patent Document 2 except that the formation portion of the antireflection film 36 is different. In the solid-state imaging device of this embodiment, the signal charge read from the sensor unit 11 to the vertical transfer unit 12 via the semiconductor layer 13 is driven in the vertical direction by driving the charge transfer unit 3 (gate electrode 31). Sequentially transferred.

  In the solid-state imaging device including the imaging unit 10 having the effective pixel region A and the OB region B like the solid-state imaging device of the present embodiment, it is particularly important to reduce the dark current.

  The light shielding films 4 and 35 and the silicon nitride film (antireflection film 36) made of metal such as aluminum (Al) or tungsten (W) constituting the imaging unit 10 of the present embodiment shield hydrogen. On the other hand, the silicon oxide films (the first oxide film 2, the second oxide film 34, and the third oxide film 37) transmit hydrogen. As a result, when the antireflection film 136 is formed on the sensor unit 111 in each of the effective pixel region A and the OB region B as in the conventional solid-state imaging device, the dark current in the OB region is high at a high temperature (80 ° C.). The value increases (see FIG. 5). The OB area B is used as a reference for the black level of the solid-state imaging device. For this reason, when the dark current value in the OB area B increases, even if the effective pixel area A is exposed to light, the signal level (black sun) is as if the light is not irradiated. As a result, the output image becomes dark.

  Therefore, in the solid-state imaging device of the present embodiment, the antireflection film 36 is formed only on the sensor unit 11a formed in the effective pixel region A, and the antireflection film is formed on the sensor unit 11b in the OB region. It has not been. For this reason, the hydrogen sintering effect in the OB region is improved by performing the hydrogen sintering process on the light receiving surface of the sensor unit 11b in the OB region B where the antireflection film 36 is not formed. Thereby, the increase (deterioration) of the dark current of the OB area | region B which generate | occur | produces at the time of high temperature (about 80 degreeC) can be suppressed. That is, the level difference of the dark current of the sensor units 11a and 11b between the effective pixel area A and the OB area B is reduced. Therefore, it is possible to reduce the darkness of the output image due to the dark current.

  In the solid-state imaging device of the present embodiment, the antireflection film 36 is preferably formed from a silicon nitride film (SiN film). Since the silicon nitride film (SiN film) effectively re-reflects the light reflected by the sensor unit 11a in the effective pixel region A, the light collection rate of the sensor unit 11a in the effective pixel region A can be further improved. it can. Therefore, it is possible to improve the hydrogen sintering effect of the OB region B while improving the sensitivity of the sensor unit 11a in the effective pixel region A.

  In the present embodiment, the interline transfer (IT) type solid-state imaging device has been described, but the type of the solid-state imaging device is not limited to this. The present invention can also be applied to, for example, a frame interline transfer (FIT) solid-state imaging device.

  The solid-state imaging device of the present invention can be applied to various electronic devices such as camera-equipped mobile phones, digital video cameras, digital still cameras, security cameras (surveillance cameras), door phones, image input cameras, scanners, and facsimiles.

(2) Manufacturing Method of Solid-State Imaging Device The manufacturing method of the solid-state imaging device of the present embodiment includes an antireflection film forming step for forming the antireflection film 36 only on the sensor unit 11 in the effective pixel region A. FIG. 2 is a cross-sectional view showing the manufacturing process of the solid-state imaging device of the present invention. In FIG. 2, each part of the semiconductor substrate 1 in FIG. 1 is omitted.

  First, as shown in FIG. 2A, a gate is formed in the effective pixel region A and OB region B on the semiconductor substrate 1 via the first oxide film 2 in the same manner as in the conventional method for manufacturing a solid-state imaging device. The electrode part 31 is formed. Then, an antireflection film 36 is formed over the entire area of the gate electrode portion 31 and the first oxide film 2. As a result, a photodiode portion (light receiving portion) / transfer gate wiring structure similar to that of the conventional solid-state imaging device is formed.

  Next, as shown in FIG. 2B, in order to process (dry etching) the antireflection film 36 only in the sensor portion 11a (not shown) in the effective pixel region A, the photoresist 6 is processed by photolithography. To do. At this time, in the conventional solid-state imaging device (see FIG. 4), the photoresist 6 for processing the antireflection film 36 is left in both the effective pixel region A and the OB region B. However, in the method for manufacturing the solid-state imaging device of the present embodiment, the photoresist 6 for processing the antireflection film 36 is not left in the OB region B as shown in FIG.

  Next, as shown in FIG. 2C, the antireflection film 36 in the region where the photoresist 6 is not formed is processed (dry etching).

  Next, as shown in FIG. 2D, according to a conventional method, before forming the light shielding film 4 that shields the entire area of the OB region B, the insulation between the gate electrode portion 31 and the light shielding film 35 and the light shielding film A second oxide film 34 is formed by a CVD method for the purpose of improving the adhesion of 35. Thereafter, a light shielding film 35 made of an Al film or a W film is deposited by sputtering or CVD.

  Next, after forming the light shielding film 35 and before forming the light shielding film 4, hydrogen sintering is performed. Thereby, both the effective pixel area A and the OB area increase the sintering effect by hydrogen equally. As a result, the increase (deterioration) of dark current in the OB (optical black) region can be suppressed even at high temperatures (about 80 ° C.), and the output image does not become dark.

  Finally, the light shielding film 4 is formed over the entire area of the OB region B, and a solid-state imaging device including the imaging unit 10 as shown in FIG. 1 is manufactured.

  In the method for manufacturing the solid-state imaging device of this embodiment, hydrogen sintering may be performed after the light shielding film 35 is formed and before the light shielding film 4 is formed. That is, the processing order of the hydrogen sinter may be either before or after the formation of the third oxide film 37 formed for the purpose of insulation between the light shielding film 35 and the light shielding film 4.

  As described above, according to the manufacturing method of the solid-state imaging device of the present embodiment, the sensor unit formed in the effective pixel region A among the effective pixel region A and the optical region (OB region) in the antireflection film forming step. The antireflection film 36 is formed only on 11a, and the antireflection film is not formed on the sensor portion 11b in the OB region B. For this reason, the hydrogen sintering effect of the OB region B where the antireflection film 36 is not formed is improved. Thereby, the increase (deterioration) of the dark current of the OB area | region B which generate | occur | produces at the time of high temperature (about 80 degreeC) can be suppressed. That is, the level difference of the dark current of the sensor unit 11 between the effective pixel area A and the OB area B is reduced. Therefore, it is possible to manufacture a solid-state imaging device that can reduce the darkness of the output image due to the dark current.

  The method for manufacturing a solid-state imaging device according to the present invention further includes a light shielding film forming step for forming the light shielding film 4 over the entire area of the OB region B and a hydrogen sintering treatment step for performing a hydrogen sintering treatment. The film forming step is preferably performed after the hydrogen sintering process.

  According to the above method, the hydrogen sintering process is performed before the light-shielding film 4 that hardly transmits hydrogen is formed in the entire OB region B. Thereby, the sintering effect by hydrogen increases in the OB region B by the hydrogen sintering process. As a result, an increase in dark current in the OB region B can be reduced. Therefore, it is possible to more reliably reduce the output image from being darkened by the dark current.

  In the antireflection film forming step, the antireflection film 36 is preferably formed by plasma CVD or low pressure CVD. According to the above method, the antireflection film 36 is formed by various CVD methods such as a plasma CVD method or a low pressure CVD method. Thereby, the light reflected by the sensor unit 11a in the effective pixel region A is effectively re-reflected, and the antireflection film 36 that can further improve the light collection rate of the sensor unit 11a in the effective pixel region A is formed. can do. Therefore, it is possible to improve the hydrogen sintering effect of the OB region B while improving the sensitivity of the sensor unit 11a in the effective pixel region A.

  In addition, this invention is not limited to embodiment mentioned above, A various change is possible in the range shown to the claim. That is, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention.

  The solid-state imaging device of the present invention can be applied to various electronic devices such as camera-equipped mobile phones, digital video cameras, digital still cameras, security cameras (surveillance cameras), door phones, image input cameras, scanners, and facsimiles.

A Effective pixel area B Optical black area (OB area)
4 light shielding film 10 imaging unit 11 sensor unit (light receiving unit)
11a Sensor section (light receiving section) of effective pixel area
11b OB area sensor unit (light receiving unit)
36 Anti-reflective coating

Claims (6)

In the solid-state imaging device in which an effective pixel region and an optical black region are formed, and each of the effective pixel region and the optical black region is provided with a light receiving unit.
A solid-state imaging device, wherein an antireflection film is formed on the light receiving portion in the effective pixel region, but no antireflection film is formed on the light receiving portion in the optical black region.   The solid-state imaging device according to claim 1, wherein the antireflection film is a silicon nitride film. In the method of manufacturing a solid-state imaging device in which an effective pixel region and an optical black region are formed, and each of the effective pixel region and the optical black region is provided with a light receiving unit.
A method for manufacturing a solid-state imaging device, comprising: forming an antireflection film on the light receiving portion in the effective pixel region, and forming an antireflection film on the light receiving portion in the optical black region, wherein the antireflection film is not formed. . A light shielding film forming step of forming a light shielding film over the entire area of the optical black region;
A hydrogen sintering process for performing hydrogen sintering,
The method for manufacturing a solid-state imaging device according to claim 3, wherein the light shielding film forming step is performed after the hydrogen sintering process.   5. The method of manufacturing a solid-state imaging device according to claim 3, wherein the antireflection film forming step forms an antireflection film by a plasma CVD method or a low pressure CVD method.   The electronic device provided with the solid-state image sensor of Claim 1 or 2.

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